We present the discovery of a long-term stable L5 ( trailing ) Neptune Trojan in data acquired to search for candidate Trans-Neptunian objects for the New Horizons spacecraft to fly by during an extended post-Pluto mission .
This Neptune Trojan , 2011 HM _ { 102 } , has the highest inclination ( 29.4 ^ { \circ } ) of any known member of this population .
It is intrinsically brighter than any single L5 Jupiter Trojan at H _ { V } \sim 8.18 .
We have determined its gri colors ( a first for any L5 Neptune Trojan ) , which we find to be similar to the moderately red colors of the L4 Neptune Trojans , suggesting similar surface properties for members of both Trojan clouds .
We also present colors derived from archival data for two L4 Neptune Trojans ( 2006 RJ _ { 103 } and 2007 VL _ { 305 } ) , better refining the overall color distribution of the population .
In this document we describe the discovery circumstances , our physical characterization of 2011 HM _ { 102 } , and this object ’ s implications for the Neptune Trojan population overall .
Finally , we discuss the prospects for detecting 2011 HM _ { 102 } from the New Horizons spacecraft during their close approach in mid- to late-2013 .